Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: neilep on 11/07/2010 11:49:19
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Dear Star-Sizeologists,
As a sheepy I of course love the sun. Out of all the stars out there the Sun has my vote for the being the best. It’s like…well big !
However, check out this youtube vid and you’ll see that in comparison to other stars our Sun is like….well small !
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Clicky HERE (http://www.youtube.com/watch?v=HEheh1BH34Q) for YouTube Linky Thing
kewl eh ?
As far as I know our Sun was made when a load of stuff spun round and "coagulated" until there was enough mass for nuclear joyness to take place and then voila !!…..the Sun was born !….Now I do realise than at the end of our Suns life it’ll grow to be rather large......but.......it will be no where as near as large as the biggest stars in the above video eh ?
So..... What I’d like to know is how do big big stars get made ?…surely as soon as they reach a similar critical mass to our sun they would go through the same process and be similar in size yes ?......though, obviously not !!......so.....why are some stars so super duper massive then ?
Thanks
Hugs & shmishes
Mwah mwah mwah
Neil
It’s Full Of Stars
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I believe that the initial size of a star depends upon the conditions inside the Giant Molecular Cloud (GMC) from which it forms.
Stars form at local concentrations within the GMCs and I understand that if the GMC is relatively non-turbulent, with few eddies or local concentrations within it, and there are no nearby active or exploding stars to send compressing shockwaves through it, then you could expect fewer and larger stars to form. However, if the GMC is more turbulent, or it is subject to shockwaves, then you'll be likely to get a greater number of smaller stars forming instead.
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I believe that the initial size of a star depends upon the conditions inside the Giant Molecular Cloud (GMC) from which it forms.
Stars form at local concentrations within the GMCs and I understand that if the GMC is relatively non-turbulent, with few eddies or local concentrations within it, and there are no nearby active or exploding stars to send compressing shockwaves through it, then you could expect fewer and larger stars to form. However, if the GMC is more turbulent, or it is subject to shockwaves, then you'll be likely to get a greater number of smaller stars forming instead.
Thank Ewe very much LeeE..Gosh !..ewe know stuff ! [:)]
So, it's probably reasonable to assume that our Sun was born in a GMC that was ' averagely ' turbulent. I gather it's because of compression waves then that force the mass to 'concentrate' and thus instigate the birth of stars.
I'd never considered that before ......
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It's not so much that there are 'compression waves', but that a 'pulse' of material shed from a nearby active star or super nova may pass through the GMC and result in transient compression as it does so. This compression may be enough to create local concentrations, or further increase the densities of already existing concentrations to the point where their gravitational force remains high enough to attract further material from the GMC after the pulse of extra-GMC material has passed.
You often see large regions of new star formation in colliding galaxies for similar reasons. While it's believed that collisions between stars and/or planets are extremely rare in galactic collisions, being so relatively tiny in comparison with the distances separating them, the GMCs, being typically ~100 light years across will certainly interact with each other.
Aha! - just found this:
In triggered star formation, one of several events might occur to compress a molecular cloud and initiate its gravitational collapse. Molecular clouds may collide with each other, or a nearby supernova explosion can be a trigger, sending shocked matter into the cloud at very high speeds. Alternatively, galactic collisions can trigger massive starbursts of star formation as the gas clouds in each galaxy are compressed and agitated by tidal forces. The latter mechanism may be responsible for the formation of globular clusters.
from: http://en.wikipedia.org/wiki/Star_formation#Cloud_collapse (http://en.wikipedia.org/wiki/Star_formation#Cloud_collapse)